AOI covering test

[CharlesAuthier]

AOI tests dont go as wanted, some of them crash inside the AOI class initialization without raising the good error.

• test_multiband_input_band_selection_from_letters
• test_multiband_input_band_selection_too_many
• the line 120-121 are ok they are there for local testing
• test_multiband_input_band_selection_too_many (the corrupt file don't exist)
• test_missing_raster
• test_wrong_split
• line 408, 413-414 are use in a test that is comment at the moment